A shallow, nearly fresh sea in northern Europe, so lightly salted that it partly freezes over each winter.
Area
377,000 km²
Ocean basin
Atlantic
Location
The brackish sea of northern Europe
Average depth
about 55 m
Maximum depth
about 459 m
Salinity
~7 ppt (one of the least salty seas)
Temperature
0°C in winter to 17°C in summer
Region
Northern Europe
About the Baltic Sea
The Baltic Sea is almost enclosed by Scandinavia, the Baltic states, Poland, Germany and Denmark, linked to the North Sea only by narrow Danish straits. So many rivers pour into it, and so little ocean water enters, that it is barely salty at all — making it the largest brackish sea on Earth. It is the home of amber, the fossilised tree resin washed up on its shores.
Did you know?
It is one of the least salty seas in the world — so close to fresh water that large parts of it freeze solid in winter.
Highlights
- The largest brackish (part-fresh) sea
- Freezes over in winter
- The ancient source of amber
Photo gallery
Life in the Baltic Sea
Creatures, seabirds and marine plants — including some of the rarest and strangest — that live in these waters.
Seabirds
Northern gannet
A big white seabird that folds its wings and dives like an arrow at 100 km/h.
Marine plants & algae
Sea lettuce
A bright-green, paper-thin edible seaweed that drapes rocky shores worldwide.
Surface & deep in the Baltic Sea
The sea is warm where the Sun reaches it and cold far below. Flip between the sunlit surface and the deep water to feel the difference — these are typical figures for a enclosed sea.
Sunlit surface
24°C
typical surface temperature
Ringed by land, enclosed seas heat up more at the surface and, cut off from the open ocean, their trapped deep water often stays comparatively warm.
Recorded range for the Baltic Sea: 0°C in winter to 17°C in summer